Actually made an account because of this comment. At times like this, I'm grateful my government mandates literature courses for fourteen year olds. The biobed is symbolic. Most obviously of the doctor's mental state. And it's not subtle. The episode explores the duality of M'Benga. The doctor and the soldier. The biobed heals people. After seeing Rah, M'Benga's PTSD is triggered hard. Intense anxiety, struggling to breathe. You see him clutch what is presumably a medical tool. The next scene you see him in, he's trying to repair biobed-2. At the end of the scene he reaches for the tool again once he learns that he'll be dining with Rah. He spars with Rah, then has another attack in the shower.
At the culmination of the episode, you see M'Benga with a case containing his effects, notably a dagger. Rah in the scene ostensibly represents healing, and the doctor doesn't reach for that this time. He reaches for the D'k tahg. The biobed is offline; he's not a doctor, he's the Butcher of J'Gal.
[And just as an aside, millennia ago, doctors and surgeons were quite separate. It's in the hippocratic oath. Doctors don't do surgery. Butchers actually would do surgery; they're skilled with knives, cleavers the removal of tissues and such. It's one of the reasons Kirk teases Dr. McCoy with the nickname sawbones; saying he doesn't know anything of medicine but butchery. So, for M'Benga, whether surgeon or soldier: butcher.]

So the final lines. You see M'Benga with another case, he puts the tool away.

Biobed two is working again. At least for now. But I know it's only a matter of time before it shuts down again. Some things break in a way that can never be repaired. Only managed.

Then you see the power flicker as the screen displays "!SYSTEM ALARM!". And he's talking about himself. Rah enters sickbay→ the biobed breaks→ Rah is killed→ the biobed is repaired. Rah enters sickbay→ the doctor breaks→ the doctor kills Rah→ the doctor is healed (but in truth not). The story is told through flashbacks because he's having flashbacks. "I told myself I don't want to go home different. My family deserves better. I see now that's impossible."

The biobed is him. Him is the biobed.
Also, shit breaks. I don't care how advanced, how much effort, how much money. Shit gonna break. Shit not gonna be replaced. How often did turbolifts break on the -D? Did they throw out the lift system and replace it? Nope. Regular maintenance. Some are just offline for repairs. So it goes.